Methods and systems disclosed herein relate generally to data compression, and more specifically compression of geospatial data, for example, but not limited to, altitude and depth or latitude and longitude, with constrained loss of fidelity.
Government agencies are responsible for maintaining global databases for the making of, for example, but not limited to, aeronautical/hydrographic charts and terrain map products. A global 100 m grid requires ˜1 Tbyte of storage space, a 10 m grid requires ˜100 Tbytes of storage space. Among other problems managing these large data sets, there are presently no compression methods in use for bathymetry grids. Unlike image compression, grid compression can retain the surface shape. Right Triangulated Integrated Networks (RTINs) have been used extensively in Computer Graphics for high-speed rendering of 3 D scenes. As this technology is mature, it has been selected as the best candidate for computationally efficient thinning of topological grids.
Significant size reduction was demonstrated using the RTIN Top Down approach (creating a RTIN from a set of points and adding in more detail/triangles as needed to preserve fidelity) Petry, F. R. et al. (2014), Right triangular irregular networks approaches for variable resolution bathymetry, submitted to Computers and Geosciences. However, the Top Down approach does not preserve the original grid points, a requirement for charting applications using topological grids. What is needed is a developed bottom-up approach, i.e. an approach that starts with a full grid and iteratively eliminates triangles (Pajarola, R. & E. Gobbetti (2007), Survey of semi-regular multi-resolution models for interactive terrain rendering, Visual Computing, 23, 583-605).
Improper tessellation can arbitrarily limit the amount of thinning possible within a given mesh. What is needed is a tessellation of triangles into a unique RTIN structure to allow for proper thinning to take place. Right-TIN creation results in a non-unique Delaunay mesh. What is needed is a process to determine valid removable vertices (also referred to herein as points) within the RTIN and the orientation of the removable edges. Improper vertex or edge removal can result in either the destabilization of the RTIN structure (a mesh that is no longer an RTIN) or an irreducible RTIN (a configuration that cannot be further reduced without becoming destabilized). What is needed is proper vertex and edge detection to ensure that all RTINs can be fully reduced. What is needed is an approach that utilizes a combination of metrics to, for example, but not limited to, retain data in the shallows while trimming flat areas of little interest.